21064644 has 24 divisors (see below), whose sum is σ = 54612320. Its totient is φ = 7021512.

The previous prime is 21064627. The next prime is 21064679. The reversal of 21064644 is 44646012.

21064644 is a `hidden beast` number, since 2 + 10 + 6 + 4 + 644 = 666.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 97414 + ... + 97629.

Almost surely, 2^21064644 is an apocalyptic number.

It is an amenable number.

21064644 is an abundant number, since it is smaller than the sum of its proper divisors (33547676).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21064644 is a wasteful number, since it uses less digits than its factorization.

21064644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 195056 (or 195048 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 27.

The square root of 21064644 is about 4589.6235139715. The cubic root of 21064644 is about 276.1752195506.

The spelling of 21064644 in words is "twenty-one million, sixty-four thousand, six hundred forty-four".